David Jones, Elizabeth Street and Kidstuff, Pitt Street, Sydney on Sunday 23 December around mid-afternoon

St Vincent’s Emergency Department in the evening Monday 24 until Christmas morning and again in the afternoon and evening on Thursday 27 December

Director Communicable Diseases at NSW Health, Dr Vicky Sheppeard said the time from exposure to the development of symptoms from measles is usually about 10-18 days.

"So people should be alert to symptoms until January 14,” Sheppeard said.

The Sydney man has since recovered and is no longer infectious.

The alert comes in the same week people in Melbourne, Brisbane and Adelaide were also confirmed to have contracted measles.

Health bodies have issued warnings for others who may have come into contact with these people over the Christmas period.

Measles is a highly-infectious communicable disease and is spread by tiny droplets generated through coughing and sneezing.

Two new cases of measles have been confirmed in people who may have been infectious when they visited popular spots around Victoria, while in unrelated cases, one man in Brisbane and a 15-year-old girl in South Australia were believed to have contracted the disease while overseas.

Victoria's health department said those patients had been potentially infectious between December 10 and December 22.

The patients visited a number of crowded areas including Melbourne Airport where a flight was taken to Canberra, as well as a David Jones store and the Queen Victoria Markets in the city.

Authorities have warned people who visited the following locations at the same time to look out for measles symptoms, particularly if they were there in the seven to 18 days prior to the onset of illness.